(svn r17239) -Change [FS#2802]: allow overbuilding the front tile of a roadstation / roaddepot with road

to be consistent with overbuilding the front tile of tunnels/bridges and also to make it easier for AIs to
connect roadstations and roaddepots to the road in front of it

src/road_cmd.cpp

@@ -516,9 +516,11 @@ CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 					if (HasTileRoadType(tile, rt)) return_cmd_error(STR_ERROR_ALREADY_BUILT);
 					break;
 
-				default:
 				case ROAD_TILE_DEPOT:
+					if ((GetAnyRoadBits(tile, rt) & pieces) == pieces) return_cmd_error(STR_ERROR_ALREADY_BUILT);
 					goto do_clear;
+
+				default: NOT_REACHED();
 			}
 			break;
 
@@ -565,6 +567,7 @@ CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 		}
 
 		case MP_STATION: {
+			if ((GetAnyRoadBits(tile, rt) & pieces) == pieces) return_cmd_error(STR_ERROR_ALREADY_BUILT);
 			if (!IsDriveThroughStopTile(tile)) goto do_clear;
 
 			RoadBits curbits = AxisToRoadBits(DiagDirToAxis(GetRoadStopDir(tile)));
@@ -575,8 +578,8 @@ CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32
 		} break;
 
 		case MP_TUNNELBRIDGE:
-			if (GetTunnelBridgeTransportType(tile) != TRANSPORT_ROAD) return CMD_ERROR;
-			if (MirrorRoadBits(DiagDirToRoadBits(GetTunnelBridgeDirection(tile))) != pieces) return CMD_ERROR;
+			if (GetTunnelBridgeTransportType(tile) != TRANSPORT_ROAD) goto do_clear;
+			if (MirrorRoadBits(DiagDirToRoadBits(GetTunnelBridgeDirection(tile))) != pieces) goto do_clear;
 			if (HasTileRoadType(tile, rt)) return_cmd_error(STR_ERROR_ALREADY_BUILT);
 			/* Don't allow adding roadtype to the bridge/tunnel when vehicles are already driving on it */
 			if (HasVehicleOnTunnelBridge(tile, GetOtherTunnelBridgeEnd(tile))) return CMD_ERROR;